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Hurricane Ophelia Forecast Discussion Number 19
2017-10-13 22:42:52| National Hurricane Center (Atlantic)
Issued at 500 PM AST Fri Oct 13 2017 000 WTNT42 KNHC 132042 TCDAT2 Hurricane Ophelia Discussion Number 19 NWS National Hurricane Center Miami FL AL172017 500 PM AST Fri Oct 13 2017 Ophelia's eye has become better defined over the past 6 hours. Although cloud tops near the inner core of the hurricane are warmer than 24 hours ago, a ring of -50 deg C or colder cloud tops still surrounds the eye. Dvorak current intensity estimates have not changed substantially, and a blend of objective and subjective classifications still supports an initial intensity of 85 kt. Little change in strength is expected while Ophelia remains a hurricane, since the relatively cool SSTs along the hurricane's path will likely be offset by low shear and cold upper-level temperatures for the next 36 h. Extratropical transition will likely begin shortly after that time, as Ophelia begins to interact with a large upper-level trough approaching from the west. The dynamical guidance suggests that Ophelia will deepen in response to the trough, and although the forecast does not explicitly show it, I can not rule out that Ophelia will briefly intensify as it undergoes extratropical transition. By 72 hours, the cyclone is expected to occlude and begin weakening, though the expansion of the wind field will result in impacts over portions of the British Isles, regardless of its exact location or strength. By 96 hours, continued weakening and interaction with land will likely cause the surface circulation to become ill-defined, and dissipation is expected shortly thereafter. Ophelia is beginning to accelerate toward the east-northeast and the initial motion estimate is 060/11 kt. Very little change has been made to the official track forecast. Ophelia is still expected to continue picking up speed on an east-northeast heading while passing south of the Azores during the next 24 to 36 hours. By 48 hours, interaction with the aforementioned upper-level trough will cause Ophelia to turn toward the northeast and approach Ireland and the western UK in about 72 h. The track guidance is tightly clustered, especially through 72 h, and the new NHC track forecast is close to the various multi-model consensus aids. Although the center of Ophelia is not expected to reach Ireland or the UK until about day 3, wind and rain effects will arrive well in advance of the cyclone center. Individuals in those locations should consult products from their local meteorological service for more information on local impacts. Tropical-storm-force winds are possible throughout the Azores beginning late Saturday or Saturday night due to an approaching cold front. Any deviation to the left of Ophelia's forecast track could bring stronger winds to the islands. Interests in the Azores should refer to products issued by the Azores Weather Forecast and Watch Center. KEY MESSAGES: 1. Ophelia is expected to become a hurricane-force post-tropical cyclone by Monday before it moves near Ireland and the United Kingdom. Direct impacts from wind and heavy rain in portions of these areas are likely, along with dangerous marine conditions. For more details on the magnitude, timing, and location of impacts from post-tropical Ophelia, residents in Ireland should refer to products issued by Met Eireann, and residents in the United Kingdom should refer to products issued by the Met Office. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 32.3N 31.8W 85 KT 100 MPH 12H 14/0600Z 33.4N 29.5W 80 KT 90 MPH 24H 14/1800Z 35.2N 25.4W 80 KT 90 MPH 36H 15/0600Z 38.2N 20.3W 80 KT 90 MPH 48H 15/1800Z 43.1N 16.0W 80 KT 90 MPH 72H 16/1800Z 53.2N 10.4W 65 KT 75 MPH...POST-TROP/EXTRATROP 96H 17/1800Z 60.5N 2.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 18/1800Z...DISSIPATED $$ Forecaster Zelinsky
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